Dermatological systems and methods with handpiece for coaxial pulse delivery and temperature sensing

ABSTRACT

Dermatological systems and methods for providing a therapeutic laser treatment using a handpiece delivering one or more therapeutic laser pulses to a target skin area along a first optical path, and sensing the temperature of the target skin area based on infrared energy radiating from the target skin area along a second optical path generally counterdirectional to the first office action, and sharing a common optical axis with the first optical path for at least a portion of the first and second optical paths. The handpiece may also provide contact cooling for a first skin area comprising the target skin area.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of and claims the benefit ofpriority to U.S. patent application Ser. No. 16/805,761, filed Feb. 29,2020, entitled “Systems and Methods for Controlling Therapeutic LaserPulse Duration,” which is incorporated by reference herein in itsentirety.

BACKGROUND OF THE INVENTION

This invention relates generally to laser-based medical treatmentsystems, and more specifically to handpieces for controlling thetemperature of a target skin area in the treatment of dermatologicalconditions.

A variety of dermatological conditions are treatable usingelectromagnetic radiation (EMR). Lasers are frequently used as an EMRsource to treat a range of conditions including acne vulgaris, abnormalpigmentation, vascular skin conditions (e.g., spider veins), wrinklesand fine lines, dyschromia, and many others. Both pulsed andcontinuous-wave (CW) laser systems have been used.

Many dermatological EMR systems use a laser to photo-thermally damage atarget tissue while preserving surrounding or adjacent non-targetedtissues or structures. The principle of selective photothermolysis,which involves thermally damaging a target tissue to promote a healingresponse, has led to the development of a variety of laser applicationsas standard of care in many medical fields including dermatology.

Damage to a target tissue during photothermolysis involves raising thetemperature of the target tissue to a damage threshold temperature for aspecified time period. For a desired level of thermal damage, there is atradeoff between the temperature the target tissue must reach and thetime that the temperature must be maintained. The same thermal damagemay be achieved using a lower temperature if the time of heating isincreased; if a higher temperature is used, a shorter heating time canachieve an equivalent thermal damage. To avoid thermal damage tonon-targeted tissue, it is desirable to limit the heating time to thethermal relaxation time (TRT) of the target tissue, which is the timerequired for the target to dissipate about 63% of the thermal energyreceived from the laser pulse. TRT is related to the size of the targetchromophore, and may range from a few nanoseconds for small chromophoressuch as tattoo ink particles, to hundreds of milliseconds for largechromophores such as leg venules. The TRT for a target tissue may beused for a particular laser system to select appropriate damagethreshold temperatures for a desired level of thermal damage. Forexample, depending upon factors such as the laser power, fluence, spotsize, etc. used in a given system, a damage threshold temperature toachieve a desired level of photothermolysis at time periodsapproximately equal to (e.g., slightly longer or shorter than) the TRTmay be selected, minimizing damage to non-target tissues.

Photothermolysis can be achieved when three conditions are met: 1) thewavelength of the laser is chosen to have a preferential absorption inthe target tissue over non-target tissue; 2) the laser pulse durationshould be equal to or less than (=<) the TRT of the target tissue; and3) the laser fluence (i.e., energy per unit area) must be sufficient toexceed the thermal damage threshold of the target tissue. Together,these principles permit laser systems to be developed that deliverenergy at specific wavelengths, pulse durations, and fluences to providecontrolled energy to damage target tissue while leaving non-targetedsurrounding tissues and structures substantially unaffected.

Selectivity as well as overall safety would be improved if thetemperature of the skin could be dynamically controlled. In particular,most laser-based dermatological treatment systems do not providereliable control of the temperature of the skin during treatment, sincepulse durations and the number of pulses applied to a target treatmentarea are typically user-selected by a user and maintained for a giventreatment session until manually changed by the user (e.g., a lasertechnician, physician, nurse, etc.). There is a need for laser-basedtreatment systems providing better control of the skin temperature. Someembodiments of the present invention achieve this by using a handpiececapable of cooling the skin surface and measuring the actual skintemperature to dynamically control the temperature during a treatment.

Ideally, thermal damage is highly localized to only the particulartarget tissue (e.g., a particular skin layer at a particular location,or particular structures such as chromophores within a skin layer at aparticular location), with nearby non-targeted tissues/structuresremaining unaffected and available to facilitate the healing response inthe targeted tissue. However, the structural complexity of the skin,which includes a variety of layers each having unique structural andfunctional characteristics, has limited the development of effectiveEMR-based treatments for many skin conditions.

Effectively reaching and limiting thermal damage to target structureswithin skin tissue by laser radiation is complicated by a variety ofintrinsic and extrinsic factors. Intrinsic factors include, withoutlimitation, the depth of the target structure within tissue and theassociated absorption of light by non-targeted structures overlying thetarget (which may involve a plurality of intervening structures eachhaving different light absorption and thermal characteristics), thescattering of light within the skin above the target, the TRT of thetarget structure and intervening non-target structures, and the removal(or non-removal) of heat by blood flowing through dermal and subdermallayers. Extrinsic factors include, also without limitation, thewavelength, pulse width, power, fluence, spot size, and othercharacteristics of the laser used to treat the target tissue orstructure.

Acne vulgaris, more commonly referred to simply as acne, is the mostcommon reason for office visits to dermatologists in the United States.Over 60 million Americans suffer from acne. Treatment options includetopical applications such as disinfectants (e.g., benzoyl peroxide),retinoids (e.g., Retin-A), and antibiotics (e.g., clindamycin anderythromycin), as well as ingested compounds such as antibiotics (e.g.,tetracycline), hormonal treatments (e.g., birth control pills),isotretinoin (Accutane, which has significant side effects), and opticaltreatments such as lasers. Laser treatments have the benefit of avoidingthe side effects and inconvenience of pharmaceuticals and topicaltreatments but, at present, have limited effectiveness for reasonsincluding the previously noted complexity of skin tissue structures andlimitations of existing laser systems. More recently, nanosphereparticles have been deposited into skin pores and/or follicles, followedby heating of the nanoparticles with laser light to treat acne.Photodynamic therapies, in which an agent is applied to the skin toincrease its sensitivity to light, have also been used in conjunctionwith laser or other light (e.g., blue light) to treat acne.

There is a need for improved laser systems having greater efficacy fortreating acne. The present invention discloses systems and methods usinglaser handpieces to achieve improved treatments for a variety of medicalconditions including, without limitation, acne. In one aspect, thepresent disclosure provides laser system having handpieces providingimproved skin temperature control to avoid damage to non-targetedstructures and more precisely control thermal damage to targetstructures. In one aspect, the disclosure provides systems and methodshaving a laser source, a handpiece to cool and deliver laser pulses to atarget skin area, and a temperature determination unit to monitor thetarget skin temperature. In one embodiment, the handpiece includesoptical elements to direct laser pulses to the target tissue along afirst optical path, and a temperature determination unit determine thesurface temperature of the target tissue using infrared (IR) energyradiated from the tissue along a second optical path. The surfacetemperature may be determined before, during, or after the delivery ofthe laser pulses. In one embodiment, the temperature of a targettemperature area is determined a plurality of times before and duringthe delivery of a laser pulse. In preferred embodiments, the first andsecond optical paths have a common optical axis for at least a portionof each optical path.

Precise temperature control of the target skin area becomes highlyimportant when the patient's skin varies in thickness or composition,such that target skin areas (e.g., spots to which one or more laserpulses are applied) may reach significantly different temperatures whenthe same laser pulse is applied to different skin areas. The disparityin skin temperatures for a pre-defined laser pulse for different skinareas is magnified when a target structure (e.g., a sebaceous gland orsebum) is deeper in the skin, because of the greater scattering andabsorption of energy by overlying tissue that occurs at greater skindepths.

Heating in tissues depends upon both the absorption of the irradiatedtissue structures for the wavelength of laser light used, as well astheir thermal relaxation times, which is a measure of how rapidly theaffected structure returns to its original temperature. By deliveringthe laser energy in a pulse with a time duration less than the TRT ofthe target tissue, highly localized heating (and destruction) of atissue target structure (e.g., melanin, sebum, sebaceous gland,collagen) can be achieved, minimizing damage to non-target structures(e.g., non-targeted skin layers, blood vessels, etc.). If the laserpulse duration is less than the TRT of the target tissue, no significantheat can escape into non-target structures, and damage to non-targetstructures is limited.

For deeper target structures such as sebaceous glands, which often rangefrom 0.3-2.0 mm (more commonly 0.5-1.0 mm) below the outer surface ofthe epidermis, damage to overlying tissue structures is difficult tocontrol or limit, since the laser energy must pass through those tissuestructures before reaching the target tissue structures. The overlyingtissue structures absorb energy depending upon their respective depthsand absorption coefficients, and undesired damage may frequently occur.In some instances, the target structures are either sufficientlyshallow, or the treatment temperature to which the target structures areraised is sufficiently low, that the heating of overlying structures maynot cause excessive damage. Even where the risk of overheating theoverlying structures of a relatively deep target is minimal, however,accurate temperature control of the target structure may be poor,resulting in overheating or underheating or the target structure,discomfort to the patient, or a combination of such undesired effects.

The skin surface may be cooled to limit the temperature increase (anddamage) to non-target overlying structures, and to limit patientdiscomfort or pain. However, existing systems lack precise control ofthe cooling process. Achieving both a desired level of photothermaldamage to deeper target structures and minimizing damage to non-targetoverlying structures has proven elusive. In many cases, the skin iscooled either too much—in which case the deeper target structure failsto reach a temperature damage threshold—or too little, in which casenon-target overlying structures are damaged and the deeper targetstructure may be excessively damaged. There is a need for laser-basedtreatment systems having improved temperature control of the coolingprocess to ensure that target structures reach a desired temperature(e.g., a thermal damage temperature) and that thermal damage tonon-target structures is minimized or controlled to an acceptable level.There is a need for dermatological laser systems that are able toefficiently treat a variety of medical conditions to achieve thesegoals.

SUMMARY

In one embodiment, the invention comprises a system for treating theskin of a patient with one or more therapeutic laser pulses, the systemcomprising: a) a laser source adapted to generate at least onetherapeutic laser pulse for application to a target skin area; b) ahandpiece optically coupled to the laser source to receive the at leastone therapeutic laser pulse from the laser source and to direct the atleast one therapeutic laser pulse to the target skin area along a firstoptical path, the handpiece comprising: 1) a first optical elementcomprising a reflective element and having a first open area throughwhich said first optical path passes, wherein the first open areacomprises one of an aperture and a slot; 2) at least a second opticalelement comprising at least one of a refractive element and a reflectiveelement, wherein the first optical path engages the at least a secondoptical element; 3) a contact cooling unit comprising a cooling windowadapted to contact and cool a first skin area of the patient from afirst temperature to a second temperature, wherein the cooling windowcomprises a thermally conductive material that is transmissive toinfrared energy and the laser pulses, the first optical path passesthrough the cooling window, and the target skin area comprises afraction of the first skin area; and c) a temperature determination unitfor determining a surface temperature of the target skin area based oninfrared energy radiated from the target skin area through the coolingwindow along a second optical path sharing a common optical axis withthe first optical path for at least a portion of the first and secondoptical paths, the temperature determination unit comprising: 1) atemperature sensing element for sensing infrared energy radiated throughthe cooling window along the second optical path, the temperaturesensing element generating a first signal indicative of the infraredenergy radiating along the second optical path, wherein the infraredenergy radiating along the second optical path engages the at least asecond optical element and is reflected by the first optical element tobe detected by the temperature sensing element; and 2) a processoradapted to determine the surface temperature of the target skin area atone or more timepoints before, during, or after the application of oneor more of therapeutic laser pulses based on the infrared energydetected by the temperature sensing element.

In one embodiment, the invention comprises a method for treating theskin of a patient with one or more therapeutic laser pulses, the methodcomprising: a) providing a laser source for generating one or moretherapeutic laser pulses as a laser therapy; b) providing a handpieceoptically coupled to the laser source to receive at least onetherapeutic laser pulse from the laser source and direct the at leastone therapeutic laser pulse to a target skin area along a first opticalpath, the handpiece comprising; 1) a first optical element comprising areflective element and having a first open area comprising one of anaperture and a slot through which the first optical path passes; 2) atleast a second optical element comprising one of a refractive elementand a reflective element; and 3) a contact cooling unit comprising acooling window adapted to contact and cool a first skin area of thepatient, wherein the cooling window comprises a thermally conductivematerial that is transmissive to infrared energy and to laser light at afirst wavelength range, and wherein a target skin area to be treated bythe at least one therapeutic laser pulse comprises a portion of thefirst skin area; c) providing a temperature determination unit adaptedto determine a surface temperature of the target skin area based oninfrared energy radiated from the target skin area through the coolingwindow along a second optical path sharing a common optical axis withthe first optical path for at least a portion of the first and secondoptical paths, the temperature determination unit comprising 1) atemperature sensing element adapted to detect infrared energy radiatedthrough the cooling window along the second optical path; and 2) aprocessor adapted to determine the surface temperature of the targetskin area based on the infrared energy detected by the temperaturesensing element; d) contacting the first skin area with the coolingwindow; e) cooling the first skin area from a first temperature to asecond temperature using the cooling window; f) generating at least onetherapeutic laser pulse having a wavelength within the first wavelengthrange using the laser source; g) receiving the at least one therapeuticlaser pulse from the laser source with the handpiece; h) applying the atleast one therapeutic laser pulse to the target skin area, thetherapeutic laser pulse passing through the first open area, engagingthe at least a second optical element, and passing through the coolingwindow along the first optical path; i) determining the surfacetemperature of the target skin area one or more times before, during orafter the application of the at least one therapeutic laser pulse by 1)receiving infrared energy radiated from the target skin area along thesecond optical path using the temperature sensing element, the infraredenergy engaging the at least a second optical element and beingreflected by the first optical element onto the temperature sensingelement; and 2) determining the surface temperature of the target skinarea with the processor based on the infrared energy received by thetemperature sensing element; j) performing at least one responsiveaction in response to determining the surface temperature of the targetskin area, selected from 1) terminating the application of the at leastone therapeutic laser pulse to the target skin area based on thedetermined surface temperature; 2) indicating the instantaneous surfacetemperature of the target skin area; 3) indicating a maximum surfacetemperature of the target skin area; 4) changing at least one parameterof the laser therapy; and 5) indicating when the surface temperature ofthe target skin area returns to a desired temperature following deliveryof one or more therapeutic laser pulses to the target skin area.

In one embodiment, the invention comprises a method for treating theskin of a patient with one or more therapeutic laser pulses, the methodcomprising: a) providing a handpiece comprising; 1) a first end forreceiving at least one therapeutic laser pulse from a laser source; 2) afirst mirror having an open area comprising one of an aperture and aslot; 3) at least one second optical element; 4) a contact cooling unitat a second end of the handpiece, comprising a cooling window forcontacting and cooling a first skin area; and 5) a temperature sensingelement adapted to detect infrared energy radiated through the coolingwindow; b) contacting the first skin area with the cooling window; c)cooling the first skin area from a first temperature to a secondtemperature using the cooling window; d) receiving at least onetherapeutic laser pulse from a laser source at the first end of thehandpiece; e) applying the at least one therapeutic laser pulse to atarget skin area within the first skin area by directing the laser pulsealong a first optical path within the handpiece, the first optical pathpassing through the open area of the first mirror, engaging the at leastone second optical element, and passing through the cooling window tothe target skin area; f) sensing infrared energy radiated from thetarget skin area along a second optical path generallycounterdirectional to the first optical path and sharing a commonoptical axis with the first optical path for at least a portion of thefirst and second optical paths, the second optical path passing from thetarget skin area through the cooling window, engaging the at least onesecond optical element, and being reflected by the first mirror onto thetemperature sensing element; and g) determining the surface temperatureof the target skin area one or more times before, during or after theapplication of the at least one therapeutic laser pulse to the targetskin area based on the infrared energy sensed by the temperature sensingelement.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional illustration of skin tissue depicting theepidermis, dermis, and hypodermis, with a laser pulse applied to aportion thereof.

FIG. 2 is a cross-sectional illustration of skin tissue depicting a hairfollicle and a sebaceous gland.

FIGS. 3A and 3B are graphs illustrating the absorption coefficients ofhuman sebum lipid, water, and melanosomes for various wavelengths oflight.

FIG. 4A is a graph illustrating a surface temperature profile of atarget skin area according to a mathematical model of a treatment with alaser pulse.

FIG. 4B is a graph illustrating a sebaceous gland temperature profilewithin a target skin area according to the mathematical model of thelaser pulse of FIG. 4A.

FIG. 5A is a graph illustrating a surface temperature profile of atarget skin area before, during, and after a laser pulse treatment withskin cooling, according to a mathematical model.

FIG. 5B is a graph illustrating a sebaceous gland temperature profilewithin a target skin area before, during, and after a laser pulsetreatment with skin cooling, according to the mathematical model of FIG.5A.

FIG. 5C is more detailed graph illustrating a surface temperatureprofile for a target skin area during treatment with a laser pulseaccording to the mathematical model of FIG. 5A.

FIGS. 6A and 6B are block diagrams of embodiments of a dermatologicaltreatment system according to the present invention.

FIGS. 7 and 8 are simplified figures of a handpiece according to anembodiment of the present invention.

FIGS. 9A and 9B are perspective views of a handpiece according to anembodiment of the present invention.

FIGS. 9C, 9E, and 9G are partially exploded views of the handpiece ofFIGS. 9A and 9B.

FIGS. 9D and 9F are optical schematics showing optical paths in thehandpiece of FIGS. 9A and 9B.

FIGS. 10A and 10B together provide a flowchart illustrating a treatmentmethod according to one embodiment of the present invention.

DESCRIPTION

Exemplary embodiments of the present disclosure are illustrated in thedrawings, which are illustrative rather than restrictive. No limitationon the scope of the technology, or on the claims that follow, is to beimplied or inferred from the examples shown in the drawings anddiscussed herein.

Treatment of many dermatological conditions involve using laser light toheat a target skin area to thermally damage a selected structure withinthe target skin area and promote a healing response. Consistentlyaccurate delivery of energy to targeted structures to achieve a desiredlevel of damage to the target structure, while minimizing the deliveryof energy and corresponding damage to non-targeted structures, hasremained an unrealized goal. The present disclosure is directed toproviding systems and methods to achieve these objectives.

As used herein “target skin area” refers to the skin receiving theenergy of a laser pulse. The target skin area may include the surfaceskin area illuminated by the laser pulse, as well as deeper structuresbeneath the surface skin area that receive at least a portion of theenergy from the laser pulse. As such, “target skin areas” treated by alaser pulse may refer to a volume of skin as opposed to a true area ofan outer surface of the epidermis.

As used herein, “surface temperature” in reference to a target skin arearefers to the temperature of the target skin area as determined ormeasured at or above the surface of the skin. In particular, whereinfrared (IR) energy radiated from a target skin area is used to measurethe temperature of the skin surface, the surface temperaturedetermination includes energy radiated from deeper in the epidermis inaddition to the outermost layer of cells. Without being bound by theory,the strong scattering effects of IR wavelengths within the epidermislimit the energy emitted and detected to the upper 100 microns, andprimarily the upper portions thereof. Consequently, “determining asurface temperature” based on detection of radiated IR energy refers tothe determination of a composite or average temperature of the upperportions (e.g., tens of microns in depth) of the epidermis, and notmerely the outermost layer of skin cells. In embodiments of the presentinvention, IR-based temperature measurements or determinations providesa reliable and precise determination of the temperature of the uppermostportion of the epidermis.

As used herein in connection with optical elements and optical energy,“engages” refers to optical contact between optical energy (e.g., alaser pulse or IR energy) and an optical element such as a lens or amirror. A laser pulse or IR energy may engage a lens by passing throughit, and engages a reflective element by being reflected of its surface.

In one aspect, the present invention comprises systems and methodshaving a handpiece for improved temperature control of a target skinarea during the delivery of one or more therapeutic laser pulses in thetreatment of a medical condition. The handpiece is configured tofacilitate the delivery of laser pulses traveling in a first directionto a target skin area, and to allow IR energy radiated from the targetskin area to travel in a second direction generally opposite(“counterdirectional”) to the first direction to detect skintemperature. The handpiece is optically coupled to a laser sourceadapted to generate at least one, and preferably a plurality, oftherapeutic laser pulses for application to the target skin area. Thehandpiece receives therapeutic laser pulses from the laser source, andincludes a cooling window for contacting and cooling a first skin areathat includes the target skin area. The cooling window is transmissiveto the laser pulses and to IR energy radiated from the target skin area.The laser pulses travel through the handpiece along a first optical pathin the first direction, and pass through the cooling window to a targetskin area within the first skin area. The system further includes atemperature determination unit that includes a temperature sensingelement and a processor for determining a surface temperature of thetarget skin area based on IR energy radiated from the target skin areathrough the cooling window along a second optical path travelling alonga second optical path generally opposite or counterdirectional to thefirst optical path. In a preferred embodiment, the first optical pathand the second optical path share a common optical axis for at least aportion of their length. The handpiece includes a reflective opticalelement located in the first optical path and having one of a slot andan aperture through which the laser pulses pass while traveling alongthe first optical path. The reflective optical element is oriented toreceive the IR energy radiated from the target skin area along thesecond optical path, and to reflect it onto the temperature sensingelement. The temperature sensing element generates a signal that isprocessed by the processor to determine the surface temperature of thetarget skin area. In a preferred embodiment, the reflective opticalelement is precisely oriented to receive IR energy from substantiallyonly the target skin area, and not other adjacent tissue within thelarger skin area cooled by the cooling window. The handpiece furthercomprises at least one second optical element within the first opticalpath, and the laser pulses engage the at least one second opticalelement. In a preferred embodiment, the at least one second opticalelement comprises a plurality of optical elements, including at leastone lens and at least one reflective element (e.g., a mirror). In astill more preferred embodiment, the IR energy radiated from the targetskin area along the second optical path also engages the plurality ofoptical elements. In various embodiments, the at least one secondoptical element may comprise elements for focusing, splitting,redirecting, collimating, or performing other operations on the laserpulses and/or IR energy.

In some embodiments, the present invention comprises systems and methodsfor determining or measuring a surface temperature of a target skin areaof a patient during a laser treatment using a handpiece that providescontact cooling of the skin and surface temperature sensing ofsubstantially only a target skin area receiving laser energy. In someembodiments, the present invention provides improved temperature controlof a target non-surface (i.e., deeper) structure in the target skin areaof a patient during the laser treatment. By providing accuratetemperature control of a target skin area during the delivery of laserpulses, the invention provides systems and methods with improvedefficacy, safety and/or comfort to patients being treated for a range ofdermatological conditions.

In one aspect, the invention provides systems and methods of controllinga temperature of a target skin area during a laser treatment to avoidone or more of overheating or excessively damaging the target area,underheating the target structure, or causing undesired damage tooverlying non-targeted structures.

In one aspect, the present invention discloses systems and methods forminimizing the temperature increase of non-target structures overlying atarget structure within a target skin area during the delivery of alaser one or a plurality of laser treatment pulses to raise the targetstructure from a first temperature to a second temperature (e.g., adamage threshold temperature).

In various embodiments, systems of the present invention may determinethe temperature of a target skin area one or a plurality of timesbefore, during, or after treatment of the target skin area using IRenergy radiated from the skin. The laser treatment may comprisecomprises one pulse, or a plurality of pulses comprising a singleheating episode of the target skin area. As used herein, a “singleheating episode” involves a plurality of pulses where the first pulseraises the temperature of the target skin area from a first or baselinetemperature immediately prior to the first pulse, and each successivepulse in the heating episode is applied before the target skin areareturns to the first or baseline temperature. Where a plurality ofpulses is used to heat the target skin area in a single heating episode,the temperature of the target skin area may be determined during apulse, between pulses, or a combination of during and between pulses ofthe single heating episode.

As used in connection with temperature determinations, “real-time”refers to temperature determinations (e.g., temperature measurements orcalculations based on data from an IR temperature sensor) performed withlittle time delay (e.g., less than 100 msec, more preferably less than 5msec, most preferably 1 msec or less) between the initiation andconclusion of temperature determination. Stated differently, real-timetemperature determinations are those made very rapidly and capable ofuse by the system to perform one or more tasks, such as terminating atreatment of a target skin area, logging the skin temperature profile vstime to a memory, or providing a warning indication to a user.

In one aspect, the invention also comprises contact cooling applied toan external surface of a first skin area to enable heating of deeperstructures (e.g., a sebaceous gland) to a damage threshold temperature,while minimizing the heating of overlying non-targeted tissuestructures. Real-time temperature determinations may occur duringbefore, during, or after the cooling of a first skin area, and may beused (e.g., by a processor executing a treatment algorithm) to perform aresponsive action such as initiating, terminating or adjusting thecooling process, initiating or terminating the delivery of one or morelaser pulses to a target skin area within the skin area being cooled, oradjusting a parameter of the laser therapy.

In one aspect, the invention comprises a method of treating a patienthaving one of more dermatological conditions including, withoutlimitation, abnormal pigmentation conditions, acne vulgaris, dyschromia,hyperhidrosis i.e., excessive sweating), pigmented lesions, vascularlesions, and wrinkles and fine lines by controlled heating of a targetskin area from a first surface temperature to a second surfacetemperature sufficient to cause thermal damage to one or more structuresin the target skin area. In one embodiment, the duration of a lasertreatment pulse is based on determining the surface temperature of thetarget skin area one or more times before, during, or after the deliveryof laser treatment pulses. In one embodiment, a laser treatment pulse isterminated when the second surface temperature reaches a valueindicative of a deeper target structure (e.g., a sweat gland) reaching adesired treatment temperature. The second surface temperaturecorresponding to the target structure reaching its treatment temperaturemay be determined prior to treatment, e.g., by thermal (mathematical)modeling of the heating of the target skin area as a function of skindepth based on the parameters of the treatment laser such as wavelength,energy flux, and thermal characteristics of the target skin area such asthermal conductivity, the absorption coefficients of various tissuestructures and/or chromophores, etc.

In one aspect, the invention comprises a method of treating a patienthaving acne vulgaris by controlled heating of a target skin area from afirst surface temperature to a second surface temperature, where thesecond surface temperature corresponds to a temperature resulting inthermal damage to one of sebum or a sebaceous gland within the targetskin area. In one embodiment, the duration of the laser treatment pulseis based on determining the surface temperature of the target skin areaa plurality of times during the delivery of one or more laser treatmentpulses. In one embodiment, the laser treatment pulse is terminated whenthe second surface temperature reaches a value indicative of the deepersebaceous gland reaching a sebaceous gland treatment temperature. Thesecond surface temperature corresponding to the sebaceous gland reachingthe sebaceous gland treatment temperature may be identified by thermalmodeling as previously discussed.

FIG. 1 is a side view illustrating a cross-sectional view of a portion100 of the skin of a patient, including the outermost epidermis 102, themiddle layer or dermis 104, and the bottom layer or hypodermis 106. Theepidermis 102 has a thickness of about 80-100 μm, which may vary frompatient to patient, and even for a single patient depending upon age,health status, and other factors. It includes up to five sub-layers (notshown) and acts as an outer barrier.

The dermis 104 has a thickness of about 1-5 mm (1000-5000 μm). Itcontains the blood vessels, nerves, hair follicles, collagen and sweatglands within the skin. Because skin conditions frequently involvestructures in the dermis, many laser systems must include sufficientenergy to penetrate into the dermis to reach those structures. Carefulselection of a number of parameters must be made in the design andconstruction of laser systems to achieve a desired level of damage to atarget structure while minimizing or avoiding damage to non-targeted(e.g., overlying) structures. For example, incorrect selection of thelaser wavelength, pulse width, energy per pulse, the use (or nonuse) ofa seed laser, or the pump energy of the laser source or amplifier mayresult in undesired damage and poor performance in treating a dermalstructure. Numerous other system choices, such as the use or non-use ofan articulating arm for delivery of the laser light to a handpiece forapplication to the skin, may also affect overall system performance.

The lowest layer of the skin is the hypodermis 106, which includesadipose tissue and collagen. The hypodermis 106 helps control bodytemperature by insulating the structures of the body below the skin. Inaddition, the hypodermis protects the inner body tissues from damage byabsorbing shock and impacts from outside the body. Because thehypodermis contains fat, its thickness varies widely from person toperson based on diet, genetic makeup, and other factors.

FIG. 1 depicts a laser beam 108 applied to a target skin area 110 of theskin 100. The target skin area 110 comprises a surface skin area 112, aswell as underlying skin tissue 114 that absorbs at least a portion ofthe energy of the laser beam 108.

FIG. 2 is a side view of the skin of a patient illustrating insimplified form, a hair 202 including a hair shaft 204 extending beyondthe exterior skin surface 206. Hair shaft 204 includes a root 208located below epidermis 210 in the dermis 212. The base, or papilla, ofroot 208 is located about 4 mm below exterior skin surface 206. Root 208is housed within hair follicle 214 and is surrounded by tissuesincluding connective tissue sheath 216 and blood vessels 218. Follicle214 includes a sebaceous gland 219 below an opening 223. Sebaceousglands such as gland 219 are typically located at depths ranging fromabout 0.3 mm (300 μm) to about 2.0 mm (2000 μm) below exterior skinsurface 206, but their depth varies depending upon body location.

Epidermis 210 includes melanin (not shown), a dark pigment found intissues of the hair, skin and eyes. Melanin, the primary determinant ofskin color, is located within globular structures known as melanosomes,which are produced by skin cells called melanocytes. Darker skin hasmore melanosomes (and thus more melanin) per unit skin area compared tolighter skin. Laser systems targeting deeper structures such assebaceous gland 219 in the dermis may present a higher risk of patientdiscomfort where wavelengths having a relatively high absorptioncoefficient in melanin are used. Without being bound by theory, whenlaser light at wavelengths readily absorbed by melanin is applied todarker skin (or dark tattoos having ink particles that absorb laserlight at similar wavelengths to melanin), the energy absorbed by themelanin (or tattoo ink particles) attenuates part of the laser energythat otherwise would reach deeper structures, heating the skin of theepidermis and/or upper dermis to a greater degree thanlighter/un-tattooed skin. Additional energy—e.g., using higher fluences,higher energy per pulse, or longer treatment times—must be applied toreach and heat deeper structures to a target treatment temperature.However, higher pulse fluences and pulse energy may compound theproblem, since the additional energy delivered in a shorter time periodwill cause the overlying skin temperature to rise even faster than usinglower fluences or energies. In addition, longer treatment times can onlydeliver more energy to the target if the energy is delivered within theTRT of the target tissue—otherwise, the additional energy largely leaksfrom the target tissue into adjacent non-target tissue.

Accordingly, in one aspect, the present invention provides lasertreatment systems to minimize discomfort by adjusting one or moretreatment parameters based on the patient's skin type. In oneembodiment, the invention provides systems and methods comprising ahandpiece for determining a skin type of a patient and automaticallyadjusting one or more treatment parameters based on the skin type of thepatient. This may involve, for patients having darker skin types, one ormore of: providing additional cooling of the patient's skin prior toapplying a laser therapy to the patient's skin; lowering a first skintemperature at which a therapy pulse is initiated and applied to thepatient's skin; lowering a fluence of a laser therapy; lowering a peakpower of the laser pulses of a laser therapy; providing a longer pulsewidth of a pulsed laser therapy; and providing a larger beam diameterfor a pulsed laser therapy.

Successful treatment of acne involves damaging sebocytes, sebum and/orsebaceous glands. This involves heating these structures to damage thegland and/or kill bacteria resident therein. Accordingly, in oneembodiment the invention provides laser light at a wavelength that ishighly absorbed by sebum, compared to competing skin chromophores (e.g.,water), to limit the damage to non-targeted tissue and concentrate thelaser energy delivered into the targeted sebaceous gland. Becausesebaceous glands are relatively deep structures located in the dermis atdepths of 300-2000 μm (0.3-2.0 mm), it is desirable to select awavelength of light capable of non-ablative penetration to these depths.

FIGS. 3A and 3B are graphs illustrating the absorption curves forseveral chromophores of interest (water, sebum, and melanosomes) atwavelengths of light for portions of the near-infrared spectrum (about750 nm-1400 nm) and the short-wavelength IR spectrum (about 1400-3000nm). FIG. 3A illustrates the absorption curve 310 for sebum, the waterabsorption curve 320, and the absorption curve 330 for melanosomes. Itwill be appreciated that in laser treatment systems directed towardconditions other than acne, e.g., tattoo removal or pigmented lesions,the absorption of other chromophores (e.g., inks of various colors,hemoglobin, etc.) will be important considerations in selecting lasertreatment system parameters such as wavelength, fluence, peak power,etc.

FIG. 3A demonstrates that the sebum absorption curve 310 has a peak atabout 1727.5 nm, meaning that sebum absorbs laser light at thiswavelength more strongly than light at other nearby wavelengths, e.g.,1650 nm or 1800 nm. The absorption coefficient of water is less thanthat of sebum in a range of from about 1693 nm to about 1742 nm, andwithin a range of from about 2280-2360 nm. The absorption coefficient ofmelanosomes exceeds that of sebum at all wavelengths less than about2225 nm, although only by a small amount at the 1727.5 nm peak forsebum, as demonstrated at point 335 of FIG. 3A, where the twoabsorptions curves approach one another. It will be appreciated bypersons of skill in the art that the concentration of sebum, water, andmelanin may vary from patient to patient for a given area, and evenwithin a particular patient depending upon the target tissuestructure(s), the hydration status of the patient, and the skin type orarea of the patient.

As shown more clearly in FIG. 3B, which is a more detailed illustrationof the absorption curves of FIG. 3A for the 1600-1800 nm wavelengthregion using like numbers for like absorption curves and peaks, theabsorption coefficient for sebum (curve 310) at a peak of about 1727.5nm (point 335) is approximately twice that of water (curve 320), and isonly slightly less than that of melanosomes (curve 330). Specifically,the absorption coefficient for melanosomes at 1727.5 is about 11.0 cm-1,and that of sebum is about 10.3 cm-1. Accordingly, in one embodiment,the invention comprises a laser providing pulsed laser light at awavelength of between 1693-1742 nm, more preferably at about 1720-1730nm, and more preferably still at about 1727.5 nm.

Referring again to FIG. 3A, the sebum absorption curve 310 has a furtherabsorption peak (340) of about 2305 nm, exceeding that of both water andmelanosomes at the same wavelength. In one embodiment, the inventioncomprises a laser providing pulsed laser light at a wavelength ofbetween about 2287-2318 nm. Although sebum strongly absorbs light at2305 nm, light at this wavelength is less suitable because itspenetration depth into skin is much less than that of light at 1727.5nm. In general, at wavelengths shown in FIGS. 3A and 3B, the penetrationof light decreases with increasing wavelength. Treatment of acne andother conditions with laser light involves multiple tradeoffs, includingthe relative absorption coefficients of target and non-targettissues/structures, penetration depth of the wavelength of interest intoskin, laser power, laser pulse fluence, pulse duration, pulse frequency,etc.

FIGS. 4A and 4B illustrate exemplary temperature profiles of the surfaceof a target skin area (FIG. 4A) and a sebaceous gland (FIG. 4B) locatedbelow the surface of the target skin area during a laser pulse accordingto a mathematical model. The laser pulse is intended to raise thetemperature of the sebaceous gland to a temperature to achieve a desiredcell population death for sebocytes. In this embodiment, the laser pulseis a tophat pulse (i.e., having a uniform intensity profile over thecovered area) with a wavelength of 1727.5 nm, a pulse duration of 30msec, a beam diameter of 2.8 mm, a power of 75 W, a pulse energy of 2.25J, and a fluence of 37 J/cm2. For purposes of illustration, the skin isdepicted as remaining at body temperature for 2 seconds prior to theapplication of the pulse, although it will be appreciated that anyarbitrary time period could be shown.

Referring to FIG. 4A, at time t=2 seconds, a single pulse of laser lighthaving the parameters noted above is initiated and applied to a targetskin area, depicted at point 420. The surface temperature of the skinrises during the pulse, as shown by line 430, to slightly above 100° C.as shown by peak 440. After the pulse is terminated, the skin surfacetemperature of the target area cools rapidly over the next severalseconds, as indicated by curve 450, falling to below 60° C. within 4seconds (t=6 seconds) after the termination of the pulse.

FIG. 4B illustrates the temperature profile of a sebaceous gland locatedat a depth of 650 μm below the skin surface in the laser pulse model ofFIG. 4A. As in FIG. 4A, the skin remains at body temperature for 2seconds (410) prior to the initiation of a single pulse (421) applied tothe target skin area. The temperature of the gland rises during thepulse (430) to a maximum temperature 440 of about 92° C.—less than thesurface skin temperature illustrated in FIG. 4A due to scattering andthe energy absorbed by the overlying tissue. Because the pulse energy at1727.5 nm is preferentially absorbed by the sebaceous gland (asdiscussed in connection with FIGS. 3A and 3B), comparatively more energyfrom the laser pulse that reaches the gland is absorbed by the oilytissue therein compared to overlying tissue containing a higher watercontent. Consequently, the temperature profile (450) of the sebaceousgland after termination of the pulse at 440 differs significantly fromthat of the skin surface temperature depicted in FIG. 4A. Although thetemperature initially falls rapidly to about 85° C., the temperaturethereafter falls more slowly than the surface temperature shown in FIG.4A.

The pulse modeled in FIGS. 4A and 4B has energy levels below thosenecessary to ablate skin tissue. Although the pulse will result inthermal damage to the sebaceous gland and could be used to treat acne,temperatures above 45-50° C. are likely to result in significantdiscomfort when they persist, as illustrated in FIG. 4A, for 4 secondsor longer. Accordingly, the pulse depicted in FIG. 4A would have limitedapplication as a viable treatment to most patients. In one embodiment,the laser pulses described in connection with FIGS. 4A and 4B result intemperatures too high to be used for treatment, although they could bemodified (e.g., by lowering pulse fluences, shortening pulse treatmenttimes, etc.) to result in skin temperatures more suitable for treatment.In one embodiment, temperatures may be lowered by skin cooling, asdescribed in connection with FIGS. 5A and 5B.

FIGS. 5A and 5B illustrate exemplary temperature profiles of a targetskin area during a laser pulse according to a different mathematicalmodel than those of FIGS. 4A-B. In the embodiment of FIGS. 5A and 5B,the laser pulse has the same parameters as those of FIGS. 4A-B(wavelength A=1727.5 nm; pulse duration=30 msec; beam diameter=2.8 mm,power=75 W; pulse energy=2.25 J; fluence=37 J/cm2). However, in FIGS. 5Aand 5B the target skin area is cooled prior to, during, and after theapplication of the laser pulse.

Although many known methods and modes of precooling the skin may beused, the embodiment of FIGS. 5A and 5B are modeled on a system having acontact cooling element applied to a first skin area that includes atarget skin area to be treated by the laser pulse. The contact coolingelement includes a cooling window that, in some embodiments, directlycontacts the first skin area, and the target skin area actuallyirradiated by the laser pulse is wholly located within the first skinarea. Although a variety of materials may be used as the contact coolingwindow, in the embodiment of FIGS. 5A and 5B, the cooling systemincludes a sapphire cooling window cooled by a thermoelectrical cooler(TEC) coupled to the window. The sapphire cooling window has a thicknessof 3 mm and a diameter of 1 inch (25.4 mm), although many differentsizes, shapes, thicknesses, and materials may be used differentembodiments. For example, although the cooling window modeled in theembodiment of FIGS. 5A and 5B was circular, other cooling window shapessuch as square, rectangular, or other polygonal or nonpolygonal shapescould be used in different embodiments and for different tissue types.The cooling window was modeled as being cooled to a temperature of 5° C.

In alternative embodiments, non-contact cooling systems (e.g., cold airor other fluid circulated onto or across the surface of a target skinarea) may be used to cool the skin. However, it is believed that thethermal resistivity of the skin, and the thermal coupling between theskin and gases such as air, typically preclude non-contact systems fromproviding adequate cooling capacity during the delivery of laser pulsesto both effectively treat deeper target structures and prevent the skinsurface from reaching temperatures likely to result in significantdiscomfort. Accordingly, contact cooling systems are preferred. In otherembodiments, evaporative cooling systems (e.g., sprayed coolantevaporating from the skin) may be used.

In FIG. 5A, the contact cooling element at 5° C. is applied to the skinat time t=0, and skin temperature falls rapidly along curve 510 to atarget temperature of about 10° C. at time t=2 second, at which point(520) the laser pulse is applied to the skin. Delivery of the laserpulse to the target skin area is continued until a target surfacetemperature 560 of the target skin area is reached (540), at which pointthe laser pulse is terminated. Because the contact cooling elementcontinues to cool the skin both during and after the laser pulse, thesurface temperature falls rapidly along curve 550 after laser pulsetermination.

FIG. 5B illustrates the temperature profile of a sebaceous gland locatedat a depth of 650 μm below the skin surface in the cooling and laserpulse delivery process of FIG. 5A. When contact cooling is applied tothe skin at time t=0, the temperature of the gland declines (curve 510),but much less rapidly than the surface temperature, depicted in FIG. 5A.The laser pulse is initiated at point 520, and the temperature of thegland rises along line 530 until the laser pulse is terminated (540).The gland temperature thereafter falls along line 550, but less rapidlythan the surface temperature decline following the pulse termination inFIG. 5A.

Because direct measurement of the gland temperature is difficult orimpossible given its depth within the skin, in embodiments of thepresent invention, surface skin temperature may be monitored as anindirect indication of the gland temperature. Because the goal of thelaser treatment is to heat the sebaceous gland to a damage thresholdtemperature, cooling the gland (as opposed to the skin surface) shown bycurve 510 in FIG. 5B is undesired, but is an unavoidable consequence ofthe protective precooling of the overlying skin tissue. Precooling theoverlying skin tissue to a desired surface temperature of about 10° C.,as shown in FIG. 5A, generates a downward cooling wave in the targetskin area, propagating from the skin surface toward the deeper tissuesin the dermis and hypodermis. The precooling process may be controlledsuch that, for a sebaceous gland in a known depth range, when the laserpulse is delivered to heat the target skin area, the precooled overlyingskin remains below a damage threshold temperature while the targetsebaceous gland reaches (or exceeds) a damage threshold temperature.This is facilitated by selecting a laser wavelength for which theabsorption coefficient of sebum/sebaceous gland tissue exceeds that ofwater, the primary chromophore of most of the overlying dermal andepidermal tissue.

Comparing FIGS. 5A and 5B, precooling the skin allows the sebaceousgland to reach a temperature of about 78° C. at the termination of thelaser pulse—about 13° C. above the surface temperature of target skinarea at the surface (about 62° C.). Although the overlying tissue isunavoidably heated during pulse delivery, careful precooling beforeinitiating the laser pulse allows the surface temperature to beprecooled to a temperature well below the sebaceous gland at pulseinitiation (about 10° C. for the skin surface vs. about 22° C. for thesebaceous gland as shown by FIGS. 5A and 5B at point 520). Thistemperature difference occurs because the cooling window creates athermal gradient between the skin surface and deeper structures as heatis removed. In addition, the pulse energy at a wavelength of 1727.5 nmis more highly absorbed by the sebaceous gland than overlying tissue.Because of the selective precooling and differential absorption betweenthe surface and the sebaceous gland, the non-targeted overlying tissueis heated by the laser pulse to a lower temperature (about 63° C., FIG.5A at point 540) than the targeted sebaceous gland (about 81° C., FIG.5B at point 540), minimizing damage to the non-targeted tissue andpatient discomfort.

In some embodiments, the present invention includes a method ofcontrolling the duration of a pulse to limit the surface temperature ofa target skin area to a desired or target threshold using a handpiececapable of contact cooling and rapid, real-time temperature measurementof the skin during the delivery of one or more laser pulses. FIG. 5Cdemonstrates a method of achieving such control by monitoring thetemperature of a pulse during the delivery of a single pulse. Thesurface temperature of the skin may be determined one or more timesduring pulse delivery, and the pulse may be terminated based on one ormore of the skin temperatures. In one embodiment, the skin temperatureis periodically determined during the pulse delivery, and the pulse isterminated when the surface skin temperature reaches (or is within adesired interval of) a threshold temperature.

FIG. 5C, illustrates a surface temperature profile during the deliveryof the laser pulse of FIG. 5A. From time t=1.99 to t=2.00 seconds, thetemperature of the skin near the surface (modeled in FIG. 5C at a depthof 100 μm) is relatively constant at about 10° C. (line 510). At timet=2.00 seconds (520), the pulse is initiated and applied to the skinthrough the cooling window. Simultaneously, the first of a plurality ofsurface temperature determinations of the target skin area 570 is made.Pulse delivery continues along line 530, and the surface temperaturerises until the pulse is terminated at 540. After pulse termination, thesurface temperature falls as indicated by line 550. During pulsedelivery, multiple temperature determinations 570 are made at equalintervals, although the frequency of temperature sampling may vary basedon a variety of factors such as the time frame desired for heating thetissue, thermal relaxation time of the target structure, pulse fluence,pulse power, pulse wavelength, and exogenous factors such as the targetstructure damage threshold, and other factors. Temperaturedeterminations may be performed at a desired sampling interval, e.g.,100 msec or less (i.e., 10 or more temperature determinations persecond) and may occur at uniform or non-uniform time intervals, e.g.,varying based on the difference between a measured temperature and adesired threshold, or on other exogenous factors. In one embodiment, thetemperature sampling interval is increased as the surface skintemperature approaches a desired temperature. Depending upon the sensingelement and processor used, the surface temperature may be determined ata sampling or time interval of 0.001-100.0 msec (i.e., 1-100,000 ρsec,or performing 10 to 1 million temperature determinations per second).

FIGS. 5A and 5B illustrate methods of treating a sebaceous glandaccording to one embodiment of the present invention. Additional detailsof treating a sebaceous glans may be found in U.S. Pat. No. 10,864,380,which is incorporated herein by reference. However, embodiments of thepresent invention may be used to treat other structures in the dermis orhypodermis (e.g., sweat glands, hair follicles, etc.) by facilitatingprecise control of surface and deeper temperatures within a target skinarea.

FIG. 6A is a schematic illustration, in block diagram form, of anembodiment of a therapeutic laser system 600 having a handpiece withcontact cooling and temperature sensing for providing therapeutic laserpulses along a first optical path that is coaxial with a second opticalpath for sensing skin temperature for at least a portion of the firstand second optical paths. A laser 610, which is preferably asemiconductor laser, provides laser pulses having a wavelength with ahigh absorption coefficient in a target tissue. The target tissue may besebaceous gland tissue, sweat gland tissue, fat, or other tissue. Laser610 is optically coupled, e.g., by an optical fiber, articulating arm,or other optical coupling elements known in the art, to a handpiece 620for delivery of one or more laser pulses to a target skin area. Althoughsemiconductor (e.g., diode) lasers are preferred, it will be appreciatedthat other laser types (e.g., fiber lasers, dye lasers, etc.) may beused in different embodiments.

Handpiece 620 includes a cooling system 622 for cooling a first skinarea that includes a target skin area within the first skin area.Cooling system 622 includes a contact cooling element comprising acooling window 628 maintained in a fixed position in contact with aheatsink portion of a thermoelectric cooler (TEC) 630 by a window frame626. Cooling window 628 may comprise any of a variety of IR-transmissivematerials, including sapphire, ZnS, diamond, ZnSe, and other thermallyconductive material that are transmissive to infrared light. Inalternative embodiments (not shown), the contact cooling element maycomprise components or structures in addition to cooling window 628,such as a copper (or other material having a high thermal conductivity)cooling element that is not light-transmissive to provide additionalcooling capacity.

TEC 630 may be a Peltier-type cooler and has a warm side and a cold side(not shown). The heatsink portion of the TEC 630 is part of the coldside and is used to remove heat from the cooling window 628 to maintainthe cooling window at desired temperature as it contacts the first skinarea. A cooling medium 632 removes heat from the hot side of the TEC 630to prevent heat buildup in handpiece 620. In one embodiment, the coolingmedium comprises circulating cold water, although other thermallyconductive fluids or other materials may be used in differentembodiments. In preferred embodiments, the cooling medium is circulatedto and from TEC 630 from a reservoir (not shown) that is not part of thehandpiece.

To ensure efficient skin cooling, it is necessary to maintain goodcontact between the skin and the cooling window 628 during treatment. Inone embodiment (not shown), the invention comprises one or more contactsensing elements to detect when the cooling window 628 is properly incontact with the first skin area. The contact sensing element(s) may becoupled to, or separate from, cooling window 628 and/or frame 626, andmay comprise, e.g., one or more electrical contacts capable of sensingelectrical activity, conductivity, or resistance of the skin indicativeof adequate skin/cooling window contact. Other contact sensing elements(e.g., ultrasonic sensors) detecting different skin parameters orfeatures associated with proper contact (e.g., force, vibration,pressure, temperature, the presence of sweat or skin oils) may also beused.

One or more skin contact indicators (not shown) may alert a user to thecontact status between the skin and cooling window 628. The skin contactindicator may indicate when the contact element(s) are—or are not—ingood contact with the first skin area and may prompt the user tomanipulate the handpiece to restore good contact when necessary. Theskin contact indicator(s) may comprise, e.g., an LED indicator onhandpiece 620 that displays a first color when good skin contact existsand a second color when the window 628 is not in proper contact with theskin. Other indicators, such as an audible sound or alarm, may also beprovided, and the system may be interlocked such that the system willnot apply (or will terminate) a laser pulse if good contact between thecooling window 268 and the skin is absent.

Handpiece 620 further includes a temperature determination unit (TDU)624 for determining a surface temperature of the target skin area. TDU624 may, in various embodiments, sense the temperature of the targetskin area one or more times before (e.g., during a precooling step),during, or after (e.g., during a postcooling step) laser pulse delivery.During delivery laser pulse(s) to a target skin area, the skin surfacetemperature may be influenced by two different heating mechanisms,including energy absorbed directly from the laser, and thermal bloomresulting from energy conducted from deeper skin tissue as the thermalenergy absorbed by deeper structures relaxes into the environment.Thermal bloom from deeper structures back to the skin surface may be asignificant cause of epidermal damage in laser systems targetingrelatively deep structures such as sebaceous or sweat glands.Therapeutic laser systems such as system 600 enable improved treatmentoutcomes by ensuring that the surface temperature of a target skin arearemains below a desired surface temperature even while heating deeperstructures to higher temperatures, minimizing both skin damage andpatient discomfort.

Temperature determination unit (TD) 624 comprises a temperature sensingelement for generating a first signal indicative of skin surfacetemperature, and a processor for processing the first signal todetermine the surface temperature. TDU 624 may sense the surfacetemperature of the target skin area one or more times before, during, orafter delivery of laser pulse(s) from laser 610. TDU 624 may be capableof sensing the surface temperature of the target skin area at from 10 to1 million times per second. In one embodiment, the temperature sensingelement of TDU 624 comprises an infrared (IR) radiation detector, shownin FIG. 9A, to detect IR energy radiating from the surface of the targetskin area through the cooling window 628, and a processor (e.g.,controller 640 as discussed below) to determine the surface temperatureof the target skin area based on data received from the temperaturedetermination unit 624. It will be appreciated that non-IR temperaturesensors (e.g., an electrical temperature sensor) 624 may be used. In theembodiment of FIG. 6A, TDU 624 is a part of the handpiece 620. In someembodiments, the temperature sensing element, the processor, or theentire TDU 624 may be located outside the handpiece. In preferredembodiments, an IR temperature sensing element is provided as part ofthe handpiece 620.

Handpiece 620 also includes a plurality of optical elements 634 tosequentially direct laser pulses along a first optical path within thehandpiece to a target skin area, and to direct IR energy from the targetskin area along a second optical path that is coaxial with and generallycounterdirectional to the first optical path for at least a portion ofboth optical paths. Additional details on embodiments of the opticalelements are provided in connection with FIGS. 9A-9F. To facilitate thecounterdirectional flow of laser and IR energy, the handpiece comprisesa first optical element (not shown) having a first open area throughwhich the first optical path passes, i.e., the laser pulses do notengage the first optical element, and pass through the first open area.In contrast to the laser pulses, however, the IR energy does engage thefirst optical element, which is preferably a reflective optical element(e.g., a mirror). The first optical element directs the IR energy fromthe target skin area to the temperature sensing element in TDU 624. Thesignal from the temperature sensing element is processed to determineskin surface temperature at a desired rate of from 10 to 1 million timesper second.

The plurality of optical elements 634 in handpiece 620 also includes atleast one second optical element (not shown), and more preferably aplurality of second optical elements, that are engaged by the laserpulses and/or IR energy from the target skin area. In one embodiment,shown in more detail in FIGS. 9A-9F, the at least one second opticalelement comprises eight (8) optical elements, with the first opticalpath (i.e., the laser pulse path) engaging all eight optical elements,and the second optical path engaging five of the optical elements inaddition to the first optical element. The optical elements may includeone or more of lenses (e.g., plano-convex lenses, turning mirrors,meniscus lenses, aspherical lenses, flat lenses, etc.), mirrors (e.g.,aspherical mirrors), or other optical elements (e.g., optical parametricoscillators) to direct the laser pulses received from the optical lasersource (e.g., via an optical fiber cable) to a target skin area. Inpreferred embodiments, the at least one second optical element comprisesa plurality of lenses (e.g., at least three lenses) and at least onemirror, and the first and second optical paths engage at least twolenses and the last least one mirror. The optical elements 634 may invarious embodiments concentrate the laser energy to a single target skinarea, or may include beam-splitting elements to split each pulse beaminto multiple beams to treat a plurality of target skin areassimultaneously.

In one embodiment (see FIGS. 7, 9C, 9E, 9G), the plurality of opticalelements 634 includes a movable scanning mirror capable of movement todirect laser pulses to different target skin areas within a first skinarea cooled by cooling window 628. The movable scanning mirror alsolimits IR energy received by TDU 624 to IR energy from substantiallyonly the target skin area to which the laser is directed at any giventime, i.e., it eliminates IR light from other skin areas within thelarger first skin area cooled by cooling window 628, which issignificantly larger than a single target skin area. In embodimentsincluding a movable scanning mirror, after a first target skin area istreated by one or more laser pulses, the scanning mirror is repositionedto direct subsequent pulses to a new (i.e., second, third, etc.) targetskin area within the larger first skin area cooled by the cooling window628. When a desired number of target skin areas have been treated at asingle cooling window position, the user may reposition the coolingwindow 628 to a new position covering a new skin area, and a differentgroup of target skin areas within the new skin area may be treated bylaser 610 using scanner in handpiece 620. In one embodiment, theposition of the movable scanning mirror may be adjusted on two or moreaxes, e.g., by one or more motors, thereby directing succeeding pulsesto different target skin areas within the first skin area, enablingtreatment of a relatively high proportion of the total area in contactwith the cooling window. In alternative embodiments, the plurality ofoptical elements 634 may not include a scanner.

Referring again to FIG. 6, system 600 further includes a controller 640,which may comprise one or more processing elements such asmicroprocessors, microcontrollers, field programmable gate arrays(FPGAs), etc. to control the operations of the laser treatment system.Controller 640 includes a pulse timing control unit 642 that controlsthe timing of the laser pulses from laser 610, including initiating thepulse at a first timepoint and terminating the pulse at a secondtimepoint. The pulse timing control unit 642 may receive data fromtemperature sensor 624, and may initiate the therapeutic laser pulse ata first timepoint based on, e.g., a manual signal from a user or adetermination that target skin area has been cooled to a desired surfacetemperature (e.g., 15° C., 10° C., 5° C., 0° C., −5° C., −10° C., etc.).Pulse timing control unit 642 may also terminate the therapeutic laserpulse at a second timepoint based on, e.g., a predetermined pulsewidthor a determination that the surface temperature of the target skin areahas reached a threshold surface temperature (e.g., indicating that adeeper target structure such as a sebaceous gland has reached a damagethreshold temperature, e.g., 60° C.-75° C.).

Controller 640 also includes a temperature sensing control unit 644 thatcontrols the operation of the TDU 624. Temperature sensing control unit644 ensures that the TDU 624 determines the surface temperature of atarget skin area at a desired (e.g., programmed or predetermined)sampling rate such as 10 or more times per second. Controller 640 maysynchronize the operations of the temperature sensing control unit 644with the pulse timing control unit 642. In one embodiment, the pulsetiming control unit 642 and the temperature sensing control unit 644 maycomprise one or more of software, firmware, or other programming codeoperating in the controller 640. In one embodiment, the pulse timingcontrol unit 642 and the temperature sensing control unit 644 maycomprise separate processors or sub-processors, and/or separateexecutable code programs comprising one or more of software, firmware,etc., within controller 640. A wide variety of hardware and softwaredesigns may be used to achieve the functions described herein, and allare considered as within the scope of the present disclosure.

Controller 640 may also control other operations within the therapeuticlaser treatment system 600 (e.g., software and firmware units andsubunits, timers, mechanical or electrical elements or subsystems,etc.). These functions may also include, without limitation, control ofthe positioning of a movable scanning mirror for determining a targetskin area, as discussed above and in greater detail in connection withFIGS. 7 and 9A-9F. Controller 640 also controls the operation of coolingsystem 622, including without limitation the temperature at which thecooling window is maintained (which may be determined by a user or bythe patient's skin type as described in connection with FIG. 6B), thecooling capacity (i.e., the thermal energy removal rate of the TEC),status alarms, etc.

A user interface 650 is preferably provided to allow a system user toselect or program one or more parameters (e.g., beam diameter or spotsize, fluence, wavelength, target temperature of the surface of thetarget skin area, cooling temperature of the target skin area at which apulse may be delivered, etc.) to control the operation of therapeuticlaser system 600. User interface 650 may also display various statusindicators and data associated with the system and/or a treatmentsession, such as the current laser parameters, duration of treatment,number of pulses delivered, etc. Controller 640 may also receive andprocess inputs from the user interface 650, and provide outputs to theuser interface. In alternative embodiments, the user interface may beomitted.

Finally, the system 600 includes a power supply 660 for providing powerto one or more of the foregoing portions of the system. In oneembodiment, power supply 660 may comprise a power supply coupled to astandard NC power outlet to convert AC to DC power at one or morevoltages, and may include a battery (e.g., for backup in the event of apower outage), a supercapacitor, etc. Power supply 660 also providespower to controller 640, which in turn includes a current-controlledpower supply for driving the laser 610 and/or other system componentsand subassemblies at rapid switching rates based on inputs from pulsetiming control unit 642, temperature sensing control unit 644, coolingsystem 622, temperature sensor 24, and scanner 634.

FIG. 6B is a block diagram of an alternative embodiment of therapeuticlaser system 600 of FIG. 6A. The therapeutic laser system of FIG. 6B iscapable of determining the skin type of a patient, and adjusting one ormore treatment parameters based thereon. Like numbers are used for likeelements in FIGS. 6A and 6B, and the discussion of FIG. 6B omits orlimits previously discussed elements of FIG. 6A for brevity and to avoidrepetition. Elements previously described in connection with FIG. 6Awill have similar functions in FIG. 6B.

The system of FIG. 6B allows one or more treatment parameters of thesystem 600 to be adjusted to minimize discomfort and/or pain to patientsthat may result from differences in skin type. Handpiece 620 includes askin typing light source 636 for applying a multi-wavelength lightsignal to determine a skin type of the patient. Although different skintyping systems may be used, in one embodiment the system 600 of FIG. 6Bdetermines a Fitzpatrick skin type of the patient. Skin typing lightsource 636 may generate noncoherent, multi-wavelength light in one ormore of the visible and IR light ranges. A skin typing light sensor 638is provided to sense a portion of the light from light source 636 thatis reflected from the skin of the patient.

Controller 640 includes a skin type determination unit 646 that receivesdata from the skin typing light sensor 638 relating to, e.g., theabsorbance or non-absorbance of the patient's skin of particularwavelengths of light from the skin typing light source 636. The skintype determination unit 646 analyzes the absorbance/non-absorbance dataand determines a skin type of the patient. Controller 640 includes logic(e.g., executable software or firmware code, not shown) to modify one ormore aspects of the laser treatment based on the patient's skin type tomaintaining the skin surface temperature below a desired maximum duringtreatment.

Without being bound by theory, patients with darker skin (i.e., a highermelanin content than lighter skin) may experience a more rapidtemperature rise as relatively more energy from laser pulses is absorbedby the more highly concentrated melanin particles. To avoid an excessivetemperature (and an increased risk of patient discomfort/pain),controller 640 may, for example, provide additional cooling (i.e.,longer cooling time) for patients with darker skin; lower a target skintemperature at which a therapy pulse is or may be initiated (e.g.,automatically initiating therapy or providing a prompt to a user whenthe skin is cooled to 5° C. for patients with darker skin instead of 10°C. for lighter-skin patients); lower a fluence of the laser pulses todeliver less energy per unit time for darker skin patients; or lower apeak power of the laser pulses of a laser therapy. The controller mayalso modify or change other parameters such as laser pulse duration andlaser spot size to ensure efficacious surface temperature control in thetreatment of a wide range of skin types.

FIGS. 6A and 6B illustrate a system according to certain embodiments ofthe invention involving cooling the skin before, during, and after pulsedelivery. Alternative embodiments of the invention include systems withno cooling of the skin, or without cooling of the skin during one ormore of the periods before, during, and after delivery of thetherapeutic laser pulse. Additional alternative embodiments includesystems in which different cooling capacities (i.e., rate of heatremoval from the skin) are used in the periods before, during, or afterdelivery of the laser pulse, and during portions of these periods.

FIG. 7 is a simplified sectional view of the interior of one embodimentof a handpiece 700 for cooling a first skin area 730, applying laserpulses to one or more target skin areas within the first skin area, anddetermining the surface temperature of the target skin area(s). Laserpulses, visually shown as a laser beam 720 at an instant of time, aredelivered to the handpiece 700 via an optical fiber 740 from a diodelaser (e.g., laser 610 of FIG. 6). After exiting optical fiber 740,pulses 720 pass along a first optical path through focusing lenses 770and an aperture in a temperature detection mirror 780. Pulses 720 areredirected by a scanning mirror 760, and pass through a cooling window710 to a target skin area within a first skin area cooled by the coolingwindow. Scanning mirror 760 may be controllable (e.g., by a motor) andrepositionable such that one or more laser pulses 720 are sequentiallydirected to a series of target skin areas within the cooling window,without moving the cooling window 710 to contact a different area ofskin 730. Scanning mirror 760 also receives IR energy traveling fromsubstantially only the target skin area, and excludes IR energy fromother (i.e., non-target) areas within the first skin area. The IR energyfrom the target skin area (not shown) travels along a second opticalpath generally counterdirectional to the first optical path, and mayoccur simultaneously with the delivery of a laser pulse.

Handpiece 700 also includes a thermoelectric cooler 750, which includesa heatsink portion (not shown) in contact with cooling window 710 tomaintain the cooling window at a desired (e.g., programmed) temperatureduring contact with the first skin area 730. Cooling window 710preferably cools the first skin area from a first surface temperature(e.g., body temperature) to a second surface temperature before laserpulses 720 are applied to the skin. In one embodiment, the first skinarea is cooled before, during, and after application of a laser pulsethereto.

Skin temperatures may be detected by infrared energy radiated generallycounterdirectionally to the laser pulses from the target skin areathrough the cooling window 710. This infrared energy is reflected byscanning mirror 760 onto temperature detector mirror 780, which focusesthe infrared energy on a detection element (not shown), which generatesa temperature signal processed by a processor to determine thetemperature of the target skin area at a desired sampling rate.

FIG. 8 is a simplified partial exploded, external view of a handpiece800 for cooling skin and applying laser pulses thereto. In oneembodiment, the internal components of FIG. 7 may be enclosed within ahousing 805. A cooling window 810 (which may be the same as coolingwindow 710 of FIG. 7) is maintained in contact with a cooling heatsink820 (which may be the same as heatsink of TEC 750 of FIG. 7) by a windowframe 830, which has no thermal function and merely maintains coolingwindow 810 in contact with heatsink portion 820. It will be appreciatedthat additional or alternative components may be included in thehandpiece of FIGS. 7 and 8, and that other similar handpiececonfigurations and geometries may be used to provide a handpieceproviding skin cooling and laser pulse delivery along a first opticalpath as well as skin temperature determination and monitoring by IRenergy traveling along a second optical path generallycounterdirectional to the first optical path.

FIGS. 9A-9F are perspective (9A, 9B), optical schematic (9D, 9F), andexploded (9C, 9E, 9G) views, respectively, of one embodiment of ahandpiece 900 for providing laser therapy to a patient's skin as part ofa laser treatment system. The handpiece 900 provides contact cooling ofthe skin, and senses skin temperature from IR energy emitted by the skinalong a second optical path that is at least partially coaxial with thefirst optical path traveled by the laser pulses. By sensing temperaturealong an optical path that is partially coaxial with the laser pulsepath, greater accuracy is achieved in sensing the temperature of onlythe target skin area—i.e., the skin actually receiving the energy of alaser pulse—as opposed to adjacent tissues not receiving laser energy.This is achieved by sensing IR energy from the skin through the contactcooling window, and by using optical elements that limit the IR energyreceived by the temperature sensor (and used to determine skintemperature) to substantially only IR energy emitted by the target skinarea. Because the temperature determination is based only on IR energyemitted from the target tissue actually receiving the laser pulses, andnot on IR energy emitted from adjacent non-target tissue that does notreceive laser pulse energy, the temperature of the target skin area isobtained with high accuracy.

FIGS. 9A and 9B are perspective views of the handpiece 900, whichincludes a proximal end 902 and a distal end 904, and comprises ahousing 910 having a shape adapted for holding by a user (e.g., aphysician or technician), and having an inner volume shielding aplurality of optical elements, discussed more fully below in connectionwith FIGS. 9C, 9E, and 9G). An optical cable 905, which comprises anoptical fiber core (not shown), is coupled to the proximal end 902 ofthe handpiece 900. Optical cable 905 is coupled to a laser source (notshown) which generates and delivers laser pulses to the handpiece 900through the cable. Optical cable 905, and specifically the optical fibertherein, terminates inside the proximal end 902 of handpiece 900 in astandard optical coupler 907 (FIGS. 9C, 9E, and 9G) such as an SMAcoupler, although other standard optical couplings may be used.

At the distal end 904 of the handpiece 900, a contact cooling unit 915includes a cooling window 920 to cool, by direct contact, a first skinarea equal in size to the cooling window. In addition to the coolingwindow 920, contact cooling unit 915 also comprises other elements morefully shown in FIG. 9C, including a cooling window heat sink 916 thatsurrounds the cooling window 920, a thermoelectric cooler (TEC) 917, anda second heat sink 918. Laser pulses from optical cable 905 pass throughhandpiece 900 along a first optical path and are applied to a targetskin area, which comprises a smaller skin area within the first skinarea cooled by the cooling window.

As shown in FIG. 9B, housing 910 of handpiece 900 includes an opticalaperture or port 914 through which laser pulses exit the housing andtravel along the first optical path through the cooling window 920 tothe target skin area. Cooling window 920 is spaced a desired distancefrom housing 910 by cooling unit 915, which also functions as a spacingmember to allow a user to visualize the area being cooled and treated bythe handpiece 900.

FIG. 9C is a partially exploded view of the interior portion ofhandpiece 900 with housing 910 removed, showing in greater detail theoptical elements, contact cooling unit, and temperature determinationunit included in the handpiece 900. In alternative embodiments, thetemperature determination unit may be separate from the handpiece 900.The handpiece 900 includes a plurality of optical elements 925, 930,923, 934, 936, 938, 940, 942, and 944 within the housing 910, althoughin alternate embodiments one or more optical elements by be locatedoutside the housing. Different combinations of these optical elementseach define the first optical path taken by laser pulses 908 to thetarget skin area (FIG. 9D) and the second optical path taken by the IRenergy from the target skin area to a temperature sensing element 950(FIG. 9E).

FIG. 9C also shows additional details of contact cooling unit 915, whichincludes a cooling window heatsink 916 surrounding the cooing window920. Heat is removed from the skin by direct contact between the firstskin area and the cooling window 920, and is passed to the heatsink 918,which is coupled to the cool side of a TEC 917 to maintain the coolingwindow 920 at a desired temperature (e.g., a user selectable temperaturein the range of −10° C. to 25° C.). TEC 917 passes heat received on itscool side from cooling window 920 via cooling window heatsink 916 to itshot side, and is removed from the TEC hot side by a second heatsink 918,which is coupled to a circulating cooling medium (not shown) such aswater.

The handpiece 900 of FIG. 9C includes a temperature determination unit,which may be a temperature determination unit 624 as shown in FIG. 6.Although the temperature determination unit of FIGS. 6 and 9C is part ofhandpiece 900, in alternative embodiments, all or portions of thetemperature determination unit may be located outside of handpiece 900.Referring again to FIG. 9C, handpiece 900 includes a temperature sensingelement 950 for receiving IR energy emitted from the target skin areathrough the contact window 920 along a second optical path generallycounterdirectional to the first optical path taken by laser pulses 908.The first and second optical paths share a common optical axis for atleast a portion of their lengths. In response to receiving IR energyfrom the target skin area, temperature determination unit determines thesurface temperature of the target skin area one or more times before,during, or after the application of the at least one therapeutic laserpulses. Temperature sensing element 950 generates a signal indicative ofthe temperature of the target skin area, and is coupled to a processor(not shown) which receives and processes the signal to determine thesurface temperature of the target skin area at a desired rate (e.g.,10-1 million times per second). The temperature determination unit thatmay determine or measure surface temperature of the target skin areabefore during, or after treatment with laser pulses 908. Operation ofthe temperature determination unit may be controlled by a temperaturesensing control unit 644 (FIG. 6).

FIG. 9D is an optical schematic showing the optical path taken by thelaser pulses 908 in passing through the handpiece to the target skinarea, and the optical elements that the laser pulses engage (e.g.,lenses through which a laser pulse passes or mirrors reflecting thepulses). FIG. 9D shows a laser pulse beam 908 exiting the optical fibercoupling 907 and passing through three plano-convex lenses 930, 932, 934before being reflected by a turning mirror 936. Plano-convex lenses 930,932, 934 in the embodiment of FIG. 9D comprising BK7, fused silicalenses, although many different lens types may be used. In analternative embodiment, lenses 930, 932, and 934 may be replaced by asingle aspherical lens (not shown). Although fixed in position in theembodiment of FIG. 9D, turning mirror 936 in alternative embodiments maycomprise a steerable mirror that is adjustable to change the angle ofreflection.

After the laser pulse beam 908 is reflected by turning mirror 936, itpasses through another plano-convex lens 938 and is reflected by a beamsteering element comprising a movable turning mirror 940 that is movableor adjustable on two axes by motors, also known as a “scanning mirror.”By moving the position of the mirror, succeeding pulses may be directedto different target skin areas within the first skin area cooled by thecooling window 920. In alternative embodiments, beam steering elementsdifferent from or in addition to the movable turning mirror 940 may beused. Plano-convex lens 938 is made of ZnSe in one embodiment, althoughother materials may be used in different embodiments. Movable turningmirror 940 reflects the laser pulse beam 908 through a meniscus lens 942and a plano-convex lens 944 before passing through cooling window 920.Meniscus lens 942 and plano-convex lens 944 comprise ZnSe in oneembodiment, but may be made of different materials in alternativeembodiments. In a further alternative embodiment, lenses 938, 942, and944 together may be replaced by a single aspherical lens (not shown).Cooling window 920 is made of a material that is transmissive to bothlaser light at the wavelength(s) output by the laser source as well asIR light emitted from the target skin area. In one embodiment, coolingwindow 920 is made of sapphire. In alternative embodiments, ZnS,diamond, or ZnSe may be used successive.

FIG. 9E is the partially exploded view of the interior portion ofhandpiece 900 shown in FIG. 9C, but includes added lines showing anexemplary laser pulse 908 to illustrate the first optical path traveledby such a pulse. For brevity, discussion of the optical elements alreadynoted in FIG. 9C is omitted. As can be seen, the laser pulse 908initially follow a path having a linear optical axis from opticalcoupler 907 to the turning mirror 936. Turning mirror 936 redirects thelaser pulse along a different linear optical axis to movable turningmirror 940, which again redirects the laser pulse along a final opticalaxis to the target skin area cooled by the cooling window 920.

FIG. 9F is an optical schematic showing the optical path taken byinfrared (IR) energy 920 emitted from a target skin area and travelingalong a second optical path, and in particular the optical elementsengaged by the IR energy in passing through the handpiece 900 to thetemperature sensing element 950. As previously noted, the second opticalpath is generally opposite to the direction of the first optical path,and is coaxial with the first optical path for at least a portion of thelength of both paths. Because the target skin area is within the firstskin area and in contact with cooling window 920, FIG. 9F shows IRenergy 926 emitted from the skin directly through cooling window 920. Asnoted in connection with FIG. 9D, cooling window 920 is transmissive tothe IR energy and is made of sapphire in the embodiment of FIGS. 9A-9F.Passing through cooling window 920, the IR energy 926 passes throughplano-convex lens 944 and meniscus lens 942 and is then reflected bymovable turning mirror (“scanning mirror”) 940. The scanning mirror 940may comprise any of a number of commercially available movable turningmirrors, such as a model MR-15-30 mirror available from OptotuneSwitzerland AG, Dietikon, Switzerland. In a given position, movableturning mirror 940 directs the laser pulses 908 to the target skin area(and not, e.g., adjacent tissue), and also reflects IR energy 926emitted in the opposite direction from substantially only the targetskin area. IR energy 926 reflected from scanning mirror 940 passesthrough plano-convex lens 938 before being reflected by turning mirror936. Convex lens 944, meniscus lens 942, movable turning mirror 940,plano-convex lens 936, and turning mirror 936 are as described inconnection with FIG. 9D, and for brevity further discussion is omittedhere.

After reflection from turning mirror 936, IR energy 926 is reflected bya first optical element comprising a concentric mirror 925 onto thetemperature sensing element 950. Concentric mirror 925 includes an openarea (e.g., an aperture or slot) through which the laser pulses 908 passwithout engaging the concentric mirror 925. From cooling window 920 toconcentric mirror 295, the second optical path taken by IR energy 926 isgenerally opposite to—but coaxial with—the first optical path taken bylaser pulses 908. As noted, highly accurate temperature measurements aremade possible by sensing IR energy 926 traveling opposite to but coaxialwith the laser pulses 908, because it enables the temperature sensingelement 950 to sense IR energy from substantially only the target skinarea (i.e., the same skin area receiving the laser pulse energy).However, it will be appreciated that the second optical path taken bythe IR energy must eventually be diverted to a non-coaxial path from thefirst optical path to reach the temperature sensing element 950, whichcannot be located in the first optical path without blocking the laserpulses 908. By including a concentric mirror 925 having an aperture,handpiece 900 allows the laser pulses 908 to pass through the concentricmirror but also allows IR energy 926 to travel along second optical paththat is initially coaxial with first optical path until being reflectedoff-axis to the first optical path onto the temperature sensing element950. Temperature sensing element 950 may comprise any of a number ofcommercially available infrared sensors, such as a modelP13243-013CA-SPL sensor available from Hamamatsu Corp., Bridgewater,N.J. In a preferred embodiment, temperature sensing element 950 includesan optical filter (e.g., a substrate transparent to the IR radiationfrom the target skin area with an optical coating) such that thetemperature sensing element reflects the wavelength(s) of the lasersource but transmits the IR energy radiated from the target skin area.

FIG. 9G is the partially exploded view of the interior portion ofhandpiece 900 shown in FIG. 9C, but includes added lines showing thepath taken by IR energy 926 emitted from the target skin area toillustrate the second optical path traveled by the IR energy to thetemperature sensing element 950. Further discussion of the opticalelements already noted in FIG. 9C is omitted. FIG. 9G depicts IR energy926 emitted from the target skin area directly through the coolingwindow 905, initially following a path having a linear optical axis fromthe target skin area to movable turning mirror 940, which reflects theIR energy 926 along a different optical axis to turning mirror 936.Turning mirror 936 again reflects the IR energy 926 along a differentoptical axis to the concentric mirror 925, which reflects the IR energyonto the temperature sensing element 950. A processor (not shown)processes the signal from temperature sensing element 950 to determinethe surface skin temperature at a desire rate. The processor may beprovided either as part of handpiece 900 or may be coupled by wire orwireless connection to temperature sensing element 950. In preferredembodiments, temperature sensing element 950 and the processorassociated with it are including in the housing 910, while in alternateembodiments one or both may be located outside the housing or separatefrom handpiece 910

FIGS. 10A and 10B together disclose one embodiment of a method 1006 oftreating the skin of a patient with one or more therapeutic laser pulsesaccording to the present disclosure, with FIG. 10A depicting steps1010-1050 and FIG. 10B depicting steps 1055-1080. The method involvesthe use of one embodiment of a laser system as described in connectionwith FIGS. 9A-9F. The method includes providing a laser source forgenerating one or more laser pulses as a laser therapy (1010), as shownin FIG. 10A. In one embodiment, the laser source comprises asemiconductor laser having a wavelength in one of the near-infraredspectrum and the short-wavelength IR spectrum.

The method also includes the step of providing a handpiece coupled tothe laser source to receive at least one therapeutic laser pulse fromthe laser source, and to direct the pulses along a first optical path toa target skin area (1020). The handpiece includes a first opticalelement, at least one second optical element, and a contact coolingunit. The first optical element includes a first open area comprisingone of an aperture and a slot through which the first optical pathpasses. In one embodiment, the first optical element may compriseconcentric mirror 925 of FIG. 9C. The at least one second opticalelement comprises one of a refracting element (e.g., a lens), and areflective element (e.g., a mirror), and may include multiple lenses andmirrors similar to handpiece 900 in FIG. 9C. The contact cooling unitcomprises a cooling window for contacting and cooling a first skin areaof the patient by direct contact. The first skin area includes a targetskin area to be treated by the at least one therapeutic laser pulse(i.e., the target skin area is the skin that actually receives theenergy of one or more therapeutic laser pulses). The cooling window ismade of a thermally conductive material that is transmissive to infraredenergy and laser light at a first wavelength range that includes thewavelength of the laser source.

Referring again to FIG. 10A, the method includes the step of providing atemperature determination unit (TDU) to determine a surface temperatureof the target skin area based on IR energy radiated from the target skinarea through the cooling window (1030). The IR energy radiates along asecond optical path that is shares a common optical axis with the firstoptical path for at least a portion of the first and second opticalpaths. The second optical path is preferably generallycounterdirectional to the first optical path for at least a portion ofthe first and second optical paths, such that the IR energy fordetermining skin temperature propagates in the opposite direction to thedirection of the laser pulse(s) for at least a portion of the secondoptical path. The TDU comprises a temperature sensing element thatdetects IR energy radiated through the cooling window along the secondoptical path, and a processor that determines the surface temperature ofthe target skin area based on the IR energy detected by the temperaturesensing element. In one embodiment, the temperature sensing element maybe the temperature sensing element 950 of FIG. 9C, which provides acontinuous or intermittent signal that is processed at a desired rate bythe processor to determine the surface temperature of the target skinarea at a desired rate (e.g., 10-1,000,000 times per second, or asampling interval of from 100 msec or less). In some embodiments, thetemperature determinations may comprise real-time temperaturemeasurements used by a processor to control the duration of the lasertherapy.

The method also includes the step of contacting the first skin area withthe cooling window (1040). This may be done by a handpiece user (e.g., aphysician or technician) bringing the cooling window into contact with askin area to be treated, which cools the first skin area in contact withthe cooling window from a first temperature to a second temperature(1045). The method further includes the step of generating, using thelaser source, at least one therapeutic laser pulse having a wavelengthwith the first wavelength range (1050), shown in FIG. 10A. The methodcontinues in FIG. 10B, with the step of receiving the at least onetherapeutic laser pulse with the handpiece (1055). The method alsoincludes the step of applying the at least one therapeutic laser pulseto the target skin area by passing the pulse along the first opticalpath through the first open area of the first optical element, engagingthe at least a second optical element, and through the cooling windowinto the target skin area (1060).

The method also includes determining the surface temperature of thetarget skin area one or more times before, during, or after theapplication of the at least one therapeutic laser pulse (1070). As partof this step, the temperature sensing element receives IR energyradiated from the target skin area along the second optical path, withthe IR energy engaging the at least a second optical element and beingreflected by the first optical element onto the temperature sensingelement. The processor determines the surface temperature of the targetskin area based on the infrared energy received by the temperaturesensing element.

In some embodiments, the TDU may determine the surface temperature ofthe target skin area a plurality of times before, during, or after theapplication of the at least one therapeutic laser pulse. As anonlimiting example, the TDU may initiate determining the surfacetemperature of the target skin area when the contact cooling windowcontacts the skin of the patient, and may determine the surfacetemperature of the target skin area once every millisecond as the skinis cooled, during the application of one or more therapeutic laserpulses to the target skin area, and after the termination of the pulsesuntil the target skin area is cooled to a desired final temperature. Inanother nonlimiting example, the TDU may determine the temperature ofthe target skin area at least one time during the delivery of atherapeutic laser pulse, and at least one time before or after thepulse. In preferred embodiments, the temperature sensing elementreceives IR energy radiated substantially only from the target skinarea, and the TDU determines the surface temperature based only on thisIR energy.

Finally, the method includes performing at least one responsive actionin response to determining the surface temperature of the target skinarea (1080). The responsive action may include one or more actionsselected from a list of responsive actions. These may include, e.g.,terminating the application of the at least one therapeutic laser pulseto the target skin area (i.e., terminating a single pulse or a sequenceof pulses), indicating (e.g., via a user interface or display) theinstantaneous surface temperature of the target skin area, indicating amaximum surface temperature of the target skin area (e.g., displayingthe maximum temperature reached during delivery of one or more pulses),changing at least one parameter of the laser therapy (e.g., reducing orincreasing the intensity or duration of therapeutic laser pulses), andindicating when the surface temperature of the target skin area returnsto a desired temperature following delivery of one or more therapeuticlaser pulses to the target skin area.

In some embodiments, step of providing a handpiece includes providing ahandpiece in which the at least a second optical element includes amirror movable in at least two axes to direct the at least onetherapeutic laser pulse to one or more desired target skin areas withinthe first skin area. The mirror may be the movable turning mirror 940described in FIG. 9C. In one embodiment, after one or more firsttherapeutic laser pulses are applied to a first target skin area withthe mirror in a first position, the mirror may be moved to a secondposition, and the method may comprise delivering subsequent laserpulse(s) to a second target skin area different from the first targetskin area, but still within the first target skin area cooled by thecooling window. In this case, the laser pulse(s) again pass along afirst optical path through the first open area, engage the mirror in thesecond position, and pass through the cooling window to the secondtarget skin areas. When the pulses are delivered to the second targetskin area, the method may also comprise determining the temperature ofthe second target skin area one or more times before, during, or afterthe delivery of the laser pulse(s) to the second target skin area byreceiving IR energy radiating from the second target skin area along thesecond optical path, engaging the mirror in the second position, andreflecting from the first optical element onto the temperature sensingelement. As previously noted, the first and second optical axes arecoaxial for at least a portion of the first and second optical paths. Ina preferred embodiment, the first and second optical paths share acommon optical axis for at least the portion of the first and secondoptical axes from the movable mirror to the cooling window.

In some embodiments, the step of providing a handpiece includesproviding a handpiece in which the at least a second optical elementincludes a plurality of lenses and at least one mirror, and the firstand second optical paths engage at least two of the plurality of lensesand the at least one mirror. In some embodiments, providing a handpiecein which the at least a second optical element incudes at least fourlenses and at least one mirror.

In some embodiments, the steps of generating at least one laser pulse,receiving the at least one pulse with the handpiece and applying it tothe target skin area are repeated until the determined surfacetemperature of the target skin area reaches a target treatmenttemperature. In some embodiments, determining the surface temperature ofthe target skin area comprises repeatedly determining the target skinarea a plurality of times during the application of a therapeutic laserpulse, and the method further comprises terminating the application ofthe laser pulse when the surface temperature of the target skin areareaches a target treatment temperature.

In various embodiments, the present invention relates to the subjectmatter of the following numbered paragraphs.

101. A system for treating the skin of a patient with one or moretherapeutic laser pulses, the system comprising:

a) a laser source adapted to generate at least one therapeutic laserpulse for application to a target skin area;

b) a handpiece optically coupled to the optical source to receive the atleast one therapeutic laser pulse from the laser source and to directthe at least one therapeutic laser pulse to the target skin area along afirst optical path, the handpiece comprising:

-   -   1) a first optical element comprising a reflective element and        having a first open area through which said first optical path        passes, wherein the first open area comprises one of an aperture        and a slot;    -   2) at least a second optical element comprising at least one of        a refractive element and a reflective element, wherein the first        optical path engages the at least a second optical element;

c) a temperature determination unit for determining a surfacetemperature of the target skin area based on infrared energy radiatedfrom the target skin area through the cooling window along a secondoptical path sharing a common optical axis with the first optical pathfor at least a portion of the first and second optical paths, thetemperature determination unit comprising:

-   -   1) a temperature sensing element for sensing infrared energy        radiated through the cooling window along the second optical        path, the temperature sensing element generating a first signal        indicative of the infrared energy radiating along the second        optical path, wherein the infrared energy radiating along the        second optical path engages the at least a second optical        element and is reflected by the first optical element to be        detected by the temperature sensing element; and    -   2) a processor adapted to determine the surface temperature of        the target skin area at one or more timepoints before, during,        or after the application of one or more of therapeutic laser        pulses based on the infrared energy detected by the temperature        sensing element.

102. The system of paragraph 101, wherein the handpiece furthercomprises:

-   -   3) a contact cooling unit comprising a cooling window adapted to        contact and cool a first skin area of the patient from a first        temperature to a second temperature, wherein the cooling window        comprises a thermally conductive material that is transmissive        to infrared energy and the laser pulses, the first optical path        passes through the cooling window, and the target skin area        comprises a fraction of the first skin area.

104. The system of paragraph 101, wherein the first optical elementcomprises a mirror, and the at least a second optical element comprisesat least one lens and at least one mirror.

201. A method for treating the skin of a patient with one or moretherapeutic laser pulses, comprising:

a) providing a handpiece having

-   -   1) a first end for receiving at least one therapeutic laser        pulse from a laser source;    -   2) a first mirror having an open area comprising one of an        aperture and a slot;    -   3) at least one second optical element;    -   4) a skin contact element at a second end of the handpiece; and    -   5) a temperature sensing element adapted to detect infrared        energy radiated through the cooling window;    -   b) contacting the first skin area with the skin contact element;    -   c) receiving at least one therapeutic laser pulse from a laser        source at the first end;    -   e) applying the at least one therapeutic laser pulse to a target        skin area within the first skin area by directing the laser        pulse along a first optical path within the handpiece, the first        optical path passing through the open area of the first mirror,        engaging the at least one second optical element, and passing        through the cooling window to the target skin area;    -   f) sensing infrared energy radiated from the target skin area        along a second optical path generally counterdirectional to the        first optical path and sharing a common optical axis with the        first optical path for at least a portion of the first and        second optical paths, the second optical path passing from the        target skin area through the cooling window, engaging the at        least one second optical element, and being reflected by the        first mirror onto the temperature sensing element;    -   g) determining the surface temperature of the target skin area        one or more times before, during, or after the application of        the at least one therapeutic laser pulse to the target skin area        based on the infrared energy sensed by the temperature sensing        element.

202. The method of paragraph 201, wherein the skin contact element is acontact cooling element.

203. The method of paragraph 202, wherein contacting the first skin areacomprises contacting the first skin area with the cooling window.

204. The method of paragraph 203, further comprising:

h) cooling the first skin area from a first temperature to a secondtemperature using the cooling window.

205. The method of paragraph 204, further comprising

i) performing at least one responsive action based on the surfacetemperature of the target skin area, the responsive action selectedfrom:

1) terminating the application of the at least one therapeutic laserpulse to the target skin area based on the determined surfacetemperature;

2) indicating the instantaneous surface temperature of the target skinarea; 3) indicating a maximum surface temperature of the target skinarea;

4) changing at least one parameter of the laser therapy; and

-   -   5) indicating when the surface temperature of the target skin        area returns to a desired temperature following delivery of one        or more therapeutic laser pulses to the target skin area.

The particular embodiments disclosed and discussed above areillustrative only, as the invention may be modified and practiced indifferent but equivalent manners apparent to those skilled in the arthaving the benefit of the teachings herein. Embodiments of the presentinvention disclosed and claimed herein may be made and executed withoutundue experimentation with the benefit of the present disclosure. Whilethe invention has been described in terms of particular embodiments, itwill be apparent to those of skill in the art that variations may beapplied to systems and apparatus described herein without departing fromthe concept and scope of the invention. Examples are all intended to benon-limiting. It is therefore evident that the particular embodimentsdisclosed above may be altered or modified and all such variations areconsidered within the scope of the invention, which are limited only bythe scope of the claims.

What is claimed is:
 1. A system for treating the skin of a patient withone or more therapeutic laser pulses, the system comprising: a) a lasersource adapted to generate therapeutic laser pulses for application to aplurality of target skin areas; b) a handpiece optically coupled to thelaser source to receive the plurality of therapeutic laser pulses fromthe laser source and to direct each therapeutic laser pulse to one ofthe plurality of target skin areas along a first optical path, whereinat least a portion of the first optical path is different for eachtarget skin area, the handpiece comprising: 1) a first optical elementcomprising a reflective element and having a reflective portion and afirst open area comprising one of an aperture and a slot, wherein thefirst open area is located in the first optical path for each targetskin area of the plurality of target skin areas; 2) at least a secondoptical element comprising a movable mirror that is movable to aplurality of different mirror positions, wherein the movable mirror islocated in the first optical path for each target skin area; 3) acontact cooling unit comprising a cooling window adapted to contact andcool a first skin area of the patient from a first temperature to asecond temperature, wherein the cooling window comprises a thermallyconductive material that is located in the first optical path for eachtarget skin area and is transmissive to infrared energy and thetherapeutic laser pulses, and each target skin area of the plurality oftarget skin areas comprises a different fraction of the first skin areacooled by the contact cooling window; and 4) a temperature sensingelement for sensing, at each of the plurality of different mirrorpositions, infrared energy radiated from substantially only a selectedone of the plurality of target skin areas through the cooling windowalong a second optical path that is generally counterdirectional to, andshares a common optical axis with, the first optical path for theselected one of the plurality of target skin areas for at least aportion of the first and second optical paths of the selected one of theplurality of target skin areas, wherein: at least a portion of thesecond optical path at each of the plurality of different mirrorpositions is different from every other second optical path; the movablemirror and the reflective portion of the first optical element arelocated in the second optical path for each of the plurality ofdifferent mirror positions; the movable mirror is positioned within thehandpiece to, at each of the plurality of different positions, directone or more laser pulses to the selected one of the target skin areasalong the first optical path, receive infrared energy radiated along thesecond optical path from substantially only the selected one of theplurality of target skin areas through the cooling window, and direct atleast a portion of the received infrared energy to the reflectiveportion of the first optical element; the reflective portion of thefirst optical element is positioned to receive the at least a portion ofthe infrared energy from the movable mirror and to reflect the infraredenergy received from the movable mirror to the temperature sensingelement; and the temperature sensing element is capable of generating afirst signal indicative of the infrared energy received from the firstoptical element; and c) a temperature determination unit for determininga surface temperature of the selected on of the plurality of target skinareas based on the infrared energy received from the first opticalelement the temperature determination unit comprising a controllercomprising at least one processor adapted to process the first signal todetermine the surface temperature of the selected one of the pluralityof target skin areas at one or more timepoints before, during, or afterthe application of one or more of the therapeutic laser pulses to theselected one of the plurality of target skin areas.
 2. The system ofclaim 1, further comprising an electric motor for moving the movablemirror in at least two axes, wherein controller controls: 1) theoperation of the motor to move the movable mirror to each of theplurality of different mirror positions, 2) the operation of the lasersource to deliver one or more therapeutic laser pulses to each selectedtarget skin area at each of the plurality of different mirror positions,and controls the temperature sensing element to determine the surfacetemperature of the selected one of the plurality of target skin areas ateach of the plurality of different mirror positions.
 3. The system ofclaim 2, wherein the handpiece further comprises: 4) a housing, whereinthe first optical element, the movable mirror, and the temperaturesensing element are located within the housing.
 4. The system of claim2, and wherein each of the plurality of different target skin areas isnon-contiguous with every other target skin area within the plurality oftarget skin areas.
 5. The system of claim 1, wherein the processordetermines the surface temperature of the selected one of the pluralityof target skin areas one or more times before, during, or after theapplication of each of the plurality of therapeutic laser pulses.
 6. Thesystem of claim 1, wherein the processor determines the surfacetemperature of the target skin area a plurality of times before, during,or after the application of one or more of the therapeutic laser pulsesat a temperature sampling time interval of 100 msec or less.
 7. Thesystem of claim 6, wherein the processor determines the surfacetemperature of the selected one of the plurality of target skin areas ata desired temperature determination rate of 10-1,000,000 times persecond.
 8. The system of claim 1, wherein the at least a second opticalelement further comprises a plurality of lenses mirror, and wherein thefirst and second optical paths of the selected one of the plurality oftarget skin areas engage at least two of the plurality of lenses.
 9. Thesystem of claim 8, wherein the at least a second optical element furthercomprises at least three lenses and at least one mirror.
 10. The systemof claim 1, wherein the handpiece further comprises the temperaturedetermination unit.
 11. A system for treating the skin of a patient withtherapeutic laser light pulses, the system comprising: a) a laser sourcecapable of generating therapeutic laser light pulses; b) a handpieceoptically coupled to the laser source to receive the therapeutic laserlight pulses, and capable of directing the therapeutic laser lightpulses to one or more target skin areas along a first optical path, thehandpiece comprising: 1) a first optical element comprising one of arefractive element and a reflective element, and having a first openarea comprising one of an aperture and a slot, wherein the first openarea is located in the first optical path; 2) at least one secondoptical element comprising a movable mirror located in the first opticalpath and movable in at least two axes for directing one or moretherapeutic laser light pulses to a selected one of the one or moretarget skin areas; 3) a contact cooling unit comprising a cooling windowadapted to contact and cool a first skin area of the patient, whereinthe cooling window is located in the first optical path and comprises athermally conductive material that is transmissive to infrared energyand the therapeutic laser light pulses, and each of the one or moretarget skin areas comprises a fraction of the first skin area; and 4) atemperature sensing element for sensing infrared energy radiated fromthe selected one of the one or more target skin areas through thecooling window along a second optical path that is generallycounterdirectional to, and shares a common optical axis with, the firstoptical path for at least a portion of the first and second opticalpaths, wherein: the first optical element and the at least one secondoptical element are located in the second optical path; the movablemirror is positioned within the handpiece to direct one or more laserpulses to the selected one of the one or more target skin areas, receiveinfrared energy radiated from substantially only the selected one of theone or more target skin areas, and direct at least a portion of thereceived infrared energy to the first optical element; the first opticalelement is positioned to receive the at least a portion of the infraredenergy from the movable mirror and to direct the received infraredenergy to the temperature sensing element; and the temperature sensingelement is capable of generating a first signal indicative of theinfrared energy; and c) a temperature determination unit for determininga surface temperature of the selected one of the one or more target skinareas based on the infrared energy radiated from the selected one of theone or more target skin areas through the cooling window along thesecond optical path, the temperature determination unit comprising: acontroller comprising at least one processor adapted to process thefirst signal to determine the surface temperature of the selected one ofthe one or more target skin areas at one or more timepoints before,during, or after the application of the therapeutic laser light pulsesto the selected one of the one or more target skin areas.
 12. The systemof claim 11, wherein the movable mirror is movable in at least two axesby an electric motor, and wherein the position of the movable reflectiveelement is controlled by the processor.
 13. The system of claim 12,wherein the handpiece further comprises: 4) a housing, wherein the firstoptical element, the scanning mirror, and the temperature sensingelement are located within the housing.
 14. The system of claim 11,wherein the at least one processor determines the surface temperature ofthe selected one of the one or more target skin areas at a plurality oftimepoints during a laser pulse.
 15. The system of claim 11, wherein theat least one processor determines the surface temperature of theselected one of the one or more target skin areas one or more timesduring the application of each therapeutic laser pulse, and at leastonce before or after the application of each therapeutic laser pulse.16. The system of claim 11, wherein the at least one processordetermines the surface temperature of the selected one of the one ormore target skin areas at a temperature sampling time interval of 100msec or less.
 17. The system of claim 16, wherein the at least oneprocessor determines the surface temperature of the selected one of theone or more target skin areas at a desired temperature determinationrate of 10-1,000,000 times per second.
 18. The system of claim 11,wherein the at least one second optical element comprises a plurality oflenses located in the first and second optical paths.
 19. The system ofclaim 18, wherein the at least a second optical element comprises atleast three lenses and at least one mirror.
 20. The system of claim 11,wherein the temperature determination unit comprises a portion of thehandpiece.
 21. A system for treating the skin of a patient withtherapeutic laser light pulses, the system comprising: a) a laser sourcecapable of generating a plurality of therapeutic laser light pulses; b)a handpiece optically coupled to the laser source to receive theplurality of therapeutic laser light pulses, and capable of directingone or more of the plurality of therapeutic laser light pulses to aselected one of a plurality of target skin areas along one of aplurality of first optical paths, wherein at least a portion of eachfirst optical path of the plurality of first optical paths is differentfrom every other first optical path for each target skin area in theplurality of target skin areas, the handpiece comprising: 1) a firstoptical element comprising one of a refractive element and a reflectiveelement, and having a first open area comprising one of an aperture anda slot, wherein the first open area is located in each of the pluralityof first optical paths; 2) at least a second optical element comprisinga movable mirror located in each first optical path of the plurality offirst optical paths, wherein the mirror is movable by an electric motorto a plurality of different positions for directing each of theplurality of therapeutic laser pulses sequentially to a selected one ofthe plurality of target skin areas; 3) a contact cooling unit comprisinga cooling window adapted to contact and cool a first skin area of thepatient, wherein the cooling window comprises a thermally conductivematerial that is located in each first optical path of the plurality offirst optical paths and is transmissive to infrared energy emitted fromthe first skin area and the therapeutic laser light, and each targetskin area of the plurality of target skin areas comprises a differentfraction of the first skin area cooled by the contact cooling unit; and4) a temperature sensing element for sensing, when the movable mirror ispositioned at each position of the plurality of different positions,infrared energy radiated from substantially only a selected one of theplurality of target skin areas through the cooling window along aselected one of a plurality of second optical paths, wherein each secondoptical path of the plurality of second optical paths is generallycounterdirectional to, and shares a common optical axis with, one of theplurality of first optical paths for at least a portion of the first andsecond optical paths, wherein: the first optical element and the movablemirror are located in each of the plurality of second optical paths; themovable mirror is positioned within the handpiece to, at each one of theplurality of different positions, direct one or more laser pulses to theselected one of the plurality of target skin areas, receive infraredenergy radiated through the cooling window from substantially only theselected one of the plurality of target skin areas, and to direct atleast a portion of the infrared energy from the selected one of theplurality of target skin areas to the first optical element; the firstoptical element is positioned to receive the at least a portion of theinfrared energy from the movable mirror and to direct the infraredenergy received from the movable mirror to the temperature sensingelement; and the temperature sensing element is capable of generating afirst signal indicative of the infrared energy received from the firstoptical element; and c) a temperature determination unit for determininga surface temperature of the selected one of the plurality of targetskin areas based on the infrared energy received from the first opticalelement, the temperature determination unit comprising a controllercomprising at least one processor adapted to process the first signal todetermine the surface temperature of the selected one of the pluralityof the target skin areas at one or more timepoints before, during, orafter the application of the therapeutic laser light to the selected oneof the plurality of target skin areas.
 22. The system of claim 21,wherein the handpiece further comprises: 4) a housing, wherein the firstoptical element, the scanning mirror, and the temperature sensingelement are located within the housing.
 23. The system of claim 21,wherein the controller controls the scanning mirror and the laser sourceand causes the scanning mirror to move to each one of the plurality ofdifferent positions to deliver one or more of the plurality of laserpulses to each of the plurality of different target skin areas, andwherein each of the different target skin areas is non-contiguous withevery other target skin area within the plurality of target skin areas.